In some applications braided conductors of copper strands made of a large number of copper wires are used to provide a flexible, bendable electrical conductor between a movable contact arm and another element such as a connecting bar or a bus bar. One example is a switch gear which is used in emergencies when the normal electrical service is down to disconnect the outside electrical service and to connect the electrical current from a diesel generating set to the building or institution's power circuits. Such equipment includes a gear switch having pivotable, electrical switch elements which are the building contacts. These switch elements include braided electrical conductors which are connected at opposite ends to a solid bar or bus bar. It is the pivotable movement of the switch element that elongates the braided conductor and high current flows through these bendable, braided copper conductors necessitating that there be a good electrical joint or interface between the ends of the braided copper conductors and the pivotable switch element and the bar.
One approach to electrically join an end of a braided copper conductor assembly and the movable switch element is to have a resistance weld therebetween. However, it has been found that the resistance weld provides a poor joint in that the electrical resistance is high at the weld, it tends to heat up and some times is structurally weak. Specification 1108 of the Underwriter Laboratory states that there is a potential for failure if the joint heats, and that resistance welded connections that heat up at an unacceptable rate and level will not pass this specification. In order to provide a better electrical conjunction between the braided conductor and the pivotal switch element, silver braze has been used to braze a joint because silver braze has a better electrical conductivity and provides greater contact area than the resistance weld. However, it has been found that when soldering or brazing as stranded braided cable strands of the copper conductor tends to absorb the molten alloy by capillary action into the braided adjacent stranding. Eventually the solder or braze alloy solidifies so that the braided cable is no longer as flexible and becomes relatively stiff adjacent the joint. The stiffened braid now restricts movement of the movable contact creating operational failure. The cable is now vulnerable to breakage under repetitive pivoting of the switch elements. The wicking-out of the braze during the resistance brazing also tends to starve the braze at the joint interface so that there is a poor electrical and thermal conduction between the ends of the braided copper conductor and the movable switch element.
Additionally, the prior art methods of trying to weld or otherwise braze directly the copper wire ends with and without fittings to the terminal surfaces on a terminal bar and on contact arms has been a relatively time-consuming and laborious process with each wire end being manually positioned and welded.
Thus, there is a need to provide a good, electrical connection at the interface between the braided conductor and a terminal surface at either one or both ends of the braided conductors and one which can be done inexpensively and quickly.
Accordingly, a general object of the present invention is to provide a new and improved electrical braided copper conductor.
Another object of the invention is to provide a new and improved process for manufacture of a densified end on the end of an electrical braided copper conductor.
A still further object of the invention is to provide a new and improved switch assembly in which there is provided a brazed or soldered connection between a densified end of a braided electrical assembly connector and a switch element.